The invention relates primarily to an anti-tack bladder made with an anti-tack rubber for use with an apparatus for manufacturing pneumatic vehicle tires, more specifically with inflatable rubber bladders conventionally used to turn ply ends over a tire bead ring and against tire plies on a tire building mandrel. Methods for making and using an anti-tack bladder and an anti-tack rubber are provided.
Tire building or assembly machines (TAMS) conventionally use rolling inflatable rubber bladders to turn up plies of rubber material that have been wrapped around a tire building mandrel, a type of rotating collapsible drum. The bladder is known as a turn-up bladder and serves to turn up the plies over a bead formed from wire cables embedded in a tough hard rubber. The rubber ply material is tacky by nature to allow the turned up plies to stick together to form the side wall of the tire. The turn-up bladders are conventionally made of various elastomeric materials such as vulcanized rubber, natural (cis-1,4-polyisoprene) and/or synthetic rubber (i.e., styrene-butadiene) or mixtures thereof. The turn-up bladders will often stick to the uncured or partially cured plies when they are rolled over the beads to form part of the tire as they are inflated, typically, with compressed air. This adhesion slows the turn-up process by impeding the retraction of the deflated turn-up bladder and also results in decreased turn-up bladder life due to erosion caused by such adhesion to the plies.
U.S. Pat. No. 4,381,331 (Johnson) discloses a solution to the above tacking problem by having a ply turn-up bladder with at least a portion of its outer surface comprising a fabric layer of spaced cords calendered, (i.e., rolling a rubber compound into the fabric on multi-roll calender machines) with a coating of unvulcanized, uncured rubbery polymer partially embedded in the rubbery polymer surface. The spaces between such cords are free of the polymer so the cords can project above this polymer surface. This arrangement allows the polymer-free cords to contact the tacky plies, thereby reducing its adhesion to the turn-up bladder. The disadvantage of this solution are the complex finishing steps associated with preparing this outer fabric layer, such as a separate heating step to additionally cure a separately applied coating, and abrading the surface of the cords to remove some of the cured polymer to expose them. Consequently the Johnson bladder is costly to make.
U.S. Pat. No. 5,213,823 (Hunt) discloses a turn-up bladder made with a high release outside layer bonded to a core sulfur-cured rubber base, wherein the outside layer is cured in a conventional manner. The high release layer is formed from a mixture or blend of polyvinyl chloride and acrylonitrile-butadiene rubber, with a plasticizer and conventional rubber compounding ingredients. One example of a polyvinyl chloride and acrylonitrile-butadiene rubber blend that has been used is xe2x80x9cParacil OZOxe2x80x9d 50, manufactured by Uniroyal, Inc. of Middlebury, Conn., USA, further described in U.S. Pat. No. 3,993,607 (Florence).
Yet another solution to the ply end tacking problem is to apply a coating to the turn-up bladder itself, such as a spray coat disclosed in U.S. Pat. No. 4,359,350 (Comper). The described coating is an aqueous lubricant containing polydimethylsiloxane, a silane, a surfactant, and optionally, a metal salt of an organic acid.
U.S. Pat. No. 5,104,477 (Williams) discloses a method to apply a surface coating of controlled release characteristics to a turn-up bladder comprising the steps of applying a releasing composition, removing a vehicle to form an adhering film, and curing the film to form the exposed release coating. The composition of the release coating is disclosed as comprising a chlorosulfonated polymer, a reinforcing filler, a green tack agent, and inert volatile solvent/diluent viscosity reducing vehicles. HYPALON, chlorosulfonated polyethylene, manufactured by E.I. duPont de Nemours and Co., of Wilmington, Del. is disclosed as a suitable chlorosulfonated polymer. Typical reinforcing fillers are carbon black, silica, fumed silica, silica dioxide and various clays known in the art, which can be used to reinforce the elastomer compositions. The green (referring to uncured, unvulcanized rubber or elastomer, not color) tack agent is typically a resin such as alkaphenol/formaldyhyde, chlorinated paraffin resins, poly(beta) terpene resins, and other resins disclosed in U.S. Pat. No. 5,104,477. Chemical curing systems are also added to the releasing composition and include sulphur-based systems containing conventional amounts of nitrogen-containing accelerator and activators known in the art. Additionally, metallic oxides such as litharge, magnesia, and sulphur bearing organic compounds and epoxy resins can be used. Typical inert, viscosity-reducing solvent/diluent vehicles are composed of organic liquids having a normal boiling point between 20-200 deg. C. These solvent vehicles function to solublize or disperse the releasing composition to enable its application as a thin film on the turn-up bladder.
One problem to be solved is that of designing an anti-tack bladder avoiding the need to coat an anti-tack material onto the surface of an already formed bladder, which would comprise an additional and more complex preparation step in manufacturing the bladder. In particular, the problem to be solved is that of departing from the use of a thin film composite to cover the bladder surface: as a matter of fact, the film(s) must be uniform and able to withstand fractures, while at the same time providing sufficient flexibility, with good adhesion to the bladder and with the ability to properly control adhesion to the ply. The production of such a film is problematic and furthermore, the curing of a film of this kind on a bladder surface is a very complex step.
Yet another problem to be solved is that of avoiding the use of the additional hazardous materials and solvents which are involved in forming a vehicle to apply the coating; such materials can in fact, pose increased environmental processing costs, as well as storage and handling safety risks.
What is desired, therefore, is an inflatable bladder with reduced adhesion to a ply, improved flexibility, better fracture resistance, all without the need to form such a material with an involved multi-step process requiring abrading, applying a separate coating material (such as a liquid, paste, or gel-like material), removal of a solvent vehicle, or depositing a final uniform coating to form the bladder""s anti-tack properties.
What is also desired, therefore, is an inflatable bladder with suitable curing and anti-tack properties for use with an apparatus for manufacturing pneumatic tires. Suitable anti-tack properties in tire manufacturing allow for quick, unimpeded release of green, cured and partially cured rubber from elastomeric structures such as flexible bladders, bags, diaphragms, sleeves, and the like. Suitable curing properties of rubber used in a bladder include high durability, good cut resistance and rebound suitable for repeated inflation and deflation cycles characteristic in pneumatic tire manufacturing. The inflatable bladder should exhibit suitable curing and anti-tack properties without any visible cracking, peeling or erosion of the anti-tack bladder body under operating conditions and parameters associated with pneumatic tire manufacturing, such as capacity, bladder life, operating pressure and/or cycle time. When a rubber material is provided with such anti-tack and curing properties the bladder can be directly manufactured from, this allows a bladder to be formed without the need of additional processing steps to impart such anti-tack properties thereby simplifying production while reducing the potential for tire manufacturing down time.
Accordingly, it is an object of the invention to provide an inflatable bladder with suitable anti-tack properties for use in pneumatic tire manufacturing which is relatively simple in construction, and comprises an anti-tack rubber the body of the bladder can be manufactured from.
Another object of the invention is to provide an anti-tack rubber with suitable anti-tack and curing properties which allow for unimpeded release of green, cured and partially cured rubber from elastomeric structures such as flexible bladders, bags, diaphragms, sleeves, and other applications which benefit from a curable rubber with anti-tack properties.
A further object of the invention is to provide an anti-tack rubber with suitable curing properties which diminishes the risk that the anti-tack composition will wear off due to erosion, cracking or fracture when used with an inflatable bladder under operating conditions associated with pneumatic tire manufacture.
Another object of the invention is to provide an anti-tack rubber having sufficient tack to adhere to the ply-ends used in conventional tire manufacture without adhering to a turn-up bladder such that the turn-up bladder is eroded by contact with the ply-ends.
Yet another object of the invention is to provide a method to make an anti-tack rubber capable of achieving the above objects which mixes at least a first rubber and an anti-tack material in a single step.
Still another object of the invention is to provide a method to make an inflatable bladder capable of achieving the above objects that comprises forming an anti-tack rubber into a first ply and adhering the first ply to an elastomeric material as part of a complete bladder manufacturing process.
Another object of the invention is to provide a method to make an inflatable bladder capable of achieving the above objects that is simpler, more efficient, and environmentally benign without the need for a multi-step curing process requiring direct coating, depositing and removing a vehicle on the bladder.
Yet another object of the invention is to provide a method to use an inflatable bladder capable of achieving the above objects that comprises inflating, contacting and deflating a bladder with an anti-tack rubber that releases from contact with cured, partially cured, or uncured tire rubber with inherently less risk of eroding, cracking or peeling. Other objects of the invention will be obvious and may in part appear hereinafter.
These and other objects are achieved by the present invention which provides: an inflatable bladder comprising a body made of an anti-tack rubber, a method to make an anti-tack rubber, a method to make an inflatable bladder with suitable anti-tack and curing properties for manufacturing pneumatic tires, and a method to use an inflatable bladder with an anti-tack rubber in manufacturing pneumatic tires and turning tire plies over a bead ring.
The inflatable bladder according to the invention comprises: an elastomeric material having an outer surface, wherein at least a portion of said outer surface comprises an anti-tack rubber, said anti-tack rubber containing a blend of a first rubber and an anti-tack composition, wherein said anti-tack rubber has suitable curing and anti-tack properties for use with an apparatus for manufacturing pneumatic tires.
A method to make an anti-tack rubber according to the invention comprises: combining a first rubber and a chlorosulfonated polyethylene; adding fillers, reinforcing agents, processing aids, and plasticizers; blending into the mix cross-linking agents, metal oxides, cure accelerators, and cure activators to form said anti-tack rubber with suitable curing properties for use with an inflatable bladder in manufacturing pneumatic tires; and forming the anti-tack rubber into a separate workable ply. More preferred blends of the anti-tack rubber contain 50 to 45 parts of a natural rubber cross-linked with 55 to 60 parts of a chlorinated polyethylene, 0.9 to 1.1 parts of phenylenediamine, and 0.9 to 1.1 parts of benzothiazyl disulfide.
The invention in one of its aspects also provides a method to make an inflatable bladder with suitable curing and anti-tack properties for manufacturing pneumatic tires. Such a method comprises the steps of: mixing at least a first rubber and a anti-tack material to form an anti-tack rubber, forming the anti-tack rubber into a ply, and adhering the anti-tack rubber to an elastomeric material of the inflatable bladder. In another embodiment, the inflatable bladder can be made entirely from a ply of the anti-tack rubber.
In another aspect, the invention provides a method to use an inflatable bladder in tire manufacturing comprising the steps of: inflating the bladder having an anti-tack rubber; contacting a rubber tire material with the bladder, and deflating the bladder with suitable cure and anti-tack properties so as to release from contact with the rubber tire material upon deflation.
In another embodiment, the invention provides a method to use the inflatable bladder specifically for turning tire plies over a bead ring comprising cycles of; wrapping tire plies on a tire building drum; positioning bead rings on the tire building drum; inflating the bladder to turn the tire plies over the bead rings; and deflating the bladder containing an anti-tack rubber with suitable cure and anti-tack properties so as to release from the tire plies upon repeated deflation cycles.
The invention and its particular features will become more apparent from the following detailed description considered with reference to the accompanying drawings and example.